Pattern Alteration: Basic FBA

When I first started altering patterns, I had no idea what I was doing, and the tutorials I found were basic outlines rather than practical “how-to” guides.  This is exactly how I perform this alteration.

An FBA or “Full Bust Alteration” is probably the commonest pattern alteration.  Most pattern companies (Big 4, I’m looking at you) draft for a B cup.  If you are larger, chances are you have funny wrinkles at your armhole, or the shoulders never fit correctly or perhaps the back is always too wide.

I suggest using your “high bust” measurement to determine the size you’ll use through the shoulders and bust.  The difference between your full bust and the pattern’s full bust tells you how much to alter the pattern, though you can “cheat.”  This is a very personal preference, don’t be afraid to change things up if you want.  Check out my guide to wearing ease.

This is a very raw approach, as soon as I learned to do it properly I knew I had to work out new dart placement and balance.  That will be the second part of this post (due next week if you’re interested).

Debi at Happy Sewing Place recently posted on “Bridging the Gap.”  It’s been following me around all week.  Altering patterns for your body with confidence is a big part of bridging the gap between competent basic sewing and being able to produce with your hands the lovely thing that lives in your head.

The gallery may not make much sense until you get your hand in and try.  If you have any questions at all, just ask.  Someone else may be thinking the same thing.  I’d also like to know what I can do to make alterations posts more useful to you in your sewing.

Tomorrow- another installment of  “What I Learned Not To Do, The Hard Way.”


  1. This will seem like a silly question but do you do a FBA if a garment is not fitting do to other reasons, like a chubby back? I have been trying to fit the Colette Rooibos dress and tried an FBA and it ended up too big. I feel kind of stuck. I’m not sure if I did the FBA incorrectly or if I need to figure out another adjustment.

    Hope that makes sense!

    • Colette patterns drafts differently from the major pattern companies.. I believe she works from a C or D sloper… At any rate, that means people who often need to do an FBA don’t for her. You might try using a larger size for the bodice back, I think that would help. :)

  2. Once I figured out this whole FBA thing, my sewing pieces started to fit so much better! It’s usually pretty easy to tweak waist and hips after you’ve cut the fabric but the chest is hard to do that with. Thanks for sharing!

  3. Great tutorial. It really cleared up a lot of questions for me. I look forward to hearing how you fix the armscye and side dart in your next post after drafting the FBA. For the line A, I think you meant parallel, not perpendicular.

  4. I’m going to be starting a wool winter coat soon, and I think I’d better get off my lazy alteration butt and do an FBA. Will check back at this when I do. :)

    • What’s the pattern number? If it’s a weirdly shaped pattern piece I’d be happy to use it to show “how to do an FBA on a weird bodice shape.” Because you’re awesome. :)

  5. I don’t want to be confrontational, but I always re-trace my armhole to match the original. I am a HH cup, and the amount the armhole changes when doing this makes it impossible to wear, and I figure it’s just my boobs that are different instead of the actual shape of my arm or shoulder.

    Thanks for the tutorial!

    • It’s really interesting you say that, I’m pleased to know that works for you. I don’t retrace the original, but I do “scoop it out” a little bit for comfort, I wonder how that varies size to size… Perhaps simply re-tracing the original is the simplest and best way. Now I want to go test it… :) That’s phase 2 FBAs.

      • I have to tighten the curve on my armscyes. They are always loose on ready to wear and flash my bra.I am currently between a G and an H but I have been up to a J when nursing. Taking too large of a pivot at the armscye will impossibly tighten and distort the arm but some tightening is necessary for most as a type of closed dart. You have to do a 3 step alteration for a truly large bust.
        Step 1- You do the FBA you describe. That will get you to a max of 1.5 to 2 inches each breast.
        Step 2- You slash and spread vertically from a hinge on the shoulder seam. You are aiming for a max of one inch over the bust on each breast. You will need to torque the pattern a little to make it roughly the same expansion at the waist as the bust. The extra width in the waist will be buried in the dart. You also will true up the shoulder seam.
        Step 3- Any further width must be added at the side seam under the arm. You will angle the addition down to the waist.

      • Neat, Dawn, that’s a new one on me… That makes sense… If you don’t mind, I’ll do a little sample of what you described and add it to the “Phase 2” Fba post. Do you have much success with “s-darts” and/or converting a large FBA into princess seams? It would have everything to do with the garment and fabric type… Hmmmmm.

  6. I have never altered an S-dart. Princess seams require a long skinny football across the bust point with width added at the princess seams. I always have to tissue fit and drape this one for myself.

  7. Pingback: Balancing Darts and Refining a Full Bust Adjustment « 3 Hours Past the Edge of the World

  8. Hi, just referencing this post again as I am about to do an FBA for the first time, but I just noticed that this method is for a pattern that already has darts. What about for one that doesn’t have darts at all? I am using B5523 and made a 14 with no FBA and it looked reallllllly bad. I should have made a 12 with an FBA of 1.5 to 2 inches. Is there a set distance from the side seam that you start the FBA alteration when there is no dart to show you where? Sorry for the long question.

    • Put the pattern piece up to your body, shoulder lined up with your shoulder (remember the seam!) and cf in the right place, and mark your bust apex. That will help guide you for drawing your “slash and spread” lines. Remember you’ll be creating an underbust dart, or you can leave the dart unsewn for a dartless/roomier fit. Does that help?

  9. Pingback: Not a pattern review: Butterick 5523 | SEWN

  10. Pingback: An FBA in process | SEWN

  11. Pingback: “Giveaway” Winners and Understanding Dart Depth « 3 Hours Past the Edge of the World

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